1. Field of the Invention
The present invention relates in general to packaging materials for use in flexible bags. In particular, the present invention relates to an improved packaging materials for use in resealable bags, such as for food, and methods of making such materials.
2. Description of the Related Art
For many years it has been known to package various products, and in particular loose food products, in flexible bags. In recent years it has become increasingly common to form such bags using the so-called form, fill, and seal technique. This technique employs a roll of flexible packaging material which is fed to an apparatus which forms the flexible bag simultaneously with placing the product within the bag. This is an extremely fast and economical approach which produces quality packages.
Regardless of the method employed to form the package, one persistent problem with such flexible bags is their poor ability to be reclosed. It is common for a single flexible bag to hold more product than is desired to be used in a single application or use. This is often the case with food items such as coffee, snack chips, etc. While such bags are provided with adequate seals upon initial forming, once these seals are first broken to open the package, it is difficult to reclose the bag to the degree desired. In such situations it is often desired to reclose the bag sufficiently to at least prevent the product from inadvertently spilling from the bag, and often a greater seal is desired to retain freshness of the product and/or prevent contamination of the product.
Various devices have been proposed to attach to the bag after opening to allow the bag to be reclosed. Certain of these devices, such as clips, are only marginally adequate in their ability to achieve the desired seal. Even where such devices work properly, there is the additional expense to obtain such devices, and the effort to find and properly employ the devices.
As an alternative, it has been proposed to form the material of the bag with means for adhesive reclosure. One example of this is shown in U.S. Pat. No. 3,454,210 to Spiegel et al. Spiegel et al. propose a packaging material having a substrate (polyester and polyethylene laminate) upon which is coated a layer of a tacky adhesive. A further, thin layer of non-tacky material (polyethylene) is then placed over the tacky layer. This sheet material is then bonded to a standard package material, with the outer, thin non-tacky layer providing an initial heat seal bond with the standard sheet packaging material.
In use, the initial heat seal has a strength and sealing quality similar to standard bags. Upon opening, however, the thin non-tacky layer ruptures about the seal and is retained upon the sheet of standard packaging material, thus revealing the tacky adhesive. The tacky adhesive at the seal area may then be used to bond the sheets together numerous times to retain freshness and prevent contamination.
With the emergence of the use of form, fill, and seal machinery, this substrate/tacky adhesive/thin non-tacky layer combination was proposed for use in such machinery. This is shown in U.S. Pat. No. 5,089,320 to Strauss et al. The basic material is substantially identical in both Strauss et al. and Spiegel et al., but in the Strauss et al. method the material is bonded to itself, as is common in "form and fill" machinery, rather than to a separate, standard, material.